Power head secondary containment leak prevention and detection system and method

ABSTRACT

A submersible turbine pump includes a power head enclosed in a casing. A vacuum source associated with the submersible turbine pump draws a vacuum in the interior space of the casing. A pressure sensor may be used to monitor the vacuum in the interior space to detect a leak in the power head or the casing. If a leak is detected, an alarm may be generated and the submersible turbine pump may be deactivated.

RELATED APPLICATIONS

This patent application is a continuation-in-part application of patentapplication Ser. No. 10/703,156, filed on Nov. 6, 2003,which is acontinuation-in-part application of patent application Ser. No.10/430,890, filed on May 6, 2003, which is a continuation-in-part ofpatent application Ser. No. 10/238,822, filed on Sep. 10, 2002, all ofwhich are hereby incorporated by reference in their entireties.

patent application Ser. No. 10/390,346 entitled “Fuel Storage Tank LeakPrevention and Detection System and Method,” filed on Mar. 17, 2003 andincluding the same inventors as included in the present application isrelated to the present application and is also incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates to detection of a leak or breach in thesecondary containment of a power head associated with a submersibleturbine pump used in a fuel dispensing environment.

BACKGROUND OF THE INVENTION

In service station environments, fuel is delivered to fuel dispensersfrom underground storage tanks (UST), sometimes referred to as fuelstorage tanks. USTs are large containers located beneath the ground thatcontain fuel. A separate UST is provided for each fuel type, such as lowoctane gasoline, high octane gasoline, and diesel fuel. In order todeliver the fuel from the USTs to the fuel dispensers, a submersibleturbine pump (STP) is provided that pumps the fuel out of the UST anddelivers the fuel through a main fuel piping conduit that runs beneaththe ground in the service station.

Due to regulatory requirements governing service stations, the main fuelpiping conduit is usually required to be double-walled piping.Double-walled piping contains an inner space that carries the fuel. Anouter annular space, also called an “interstitial space,” surrounds theinner space so as to capture and contain any leaks that occur in theinner space, so that such leaks do not reach the ground. An example of adouble-walled fuel pipe is disclosed in U.S. Pat. No. 5,527,130,incorporated herein by reference in its entirety.

It is possible that the outer annular space of the double-walled fuelpiping could fail, thereby leaking fuel outside of the fuel piping ifthe inner space were to fail as well. Fuel sump sensors that detectleaks are located underneath the ground in the STP sump and the fueldispenser sumps. These sensors detect any leaks that occur in the fuelpiping at the location of the sensors. However, if a leak occurs in thedouble-walled fuel piping between these sensors, it is possible that aleak in the double-walled fuel piping will go undetected since theleaked fuel will leak into the ground, never reaching one of the fuelleak sensors. The STP will continue to operate as normal, drawing fuelfrom the UST; however, the fuel may leak to the ground instead of beingdelivered to the fuel dispensers.

Therefore, there exists a need to be able to monitor the double-walledfuel piping to determine if there is a leak or breach in the outer wall.Detection of a leak or breach in the outer wall of the double-walledfuel piping can be used to generate an alarm or other measure so thatpreventive measures can be taken to correct the leak or breach in theouter wall of the double-walled piping before a leak in the inner pipingcan escape to the ground.

Recent proposed changes in state and federal regulations will tightenthe requirements to contain leaks and will further require better leakdetection so that environmental damage may be minimized. As a result, itis becoming imperative that all potential leak sources be evaluated andsteps taken to detect and contain leaks in the piping systems. One areathat has not been specifically addressed by the parent disclosures iswithin the casing that houses the power head associated with asubmersible turbine pump.

SUMMARY OF THE INVENTION

The parent disclosures relate to a sensing unit and a tank monitor thatmonitors the vacuum level in the outer annular space of thedouble-walled fuel piping to determine if a breach or leak exists in theouter wall of the fuel piping. If the outer annular space cannotmaintain a pressure or vacuum level over a given amount of time afterbeing pressurized, this is indicative that the outer wall of the fuelpiping contains a breach or leak. If the inner conduit of the fuelpiping were to incur a breach or leak such that fuel reaches the outerannular space of the fuel piping, this same fuel would also have thepotential to reach the ground through the breach in the outer wall inthe fuel piping.

A sensing unit is provided that is communicatively coupled to a tankmonitor or other control system. The sensing unit contains a pressuresensor that is coupled to vacuum tubing. The vacuum tubing is coupled tothe outer annular space of the fuel piping, and is also coupled to apower head associated with a submersible turbine pump (STP) so that thepower head can be used as a vacuum source to generate a vacuum level inthe vacuum tubing and the outer annular space. The sensing unit and/ortank monitor determines if there is a leak or breach in the outerannular space by generating a vacuum in the outer annular space usingthe vacuum source of the power head. Subsequently, the outer annularspace is monitored using a pressure sensor to determine if the vacuumlevel changes significantly to indicate a leak. The system checks forboth catastrophic and precision leaks.

In one leak detection embodiment of the present invention, the powerhead provides a vacuum source to the vacuum tubing and the outer annularspace of the fuel piping. The tank monitor receives the vacuum level ofthe outer annular space via the measurements from the pressure sensorand the sensing unit. After the vacuum level in the outer annular spacereaches a defined initial threshold vacuum level, the vacuum of thepower head is deactivated and isolated from the outer annular space. Thevacuum level of the outer annular space is monitored. If the vacuumlevel decays to a catastrophic threshold vacuum level, the vacuum of thepower head is activated to restore the vacuum level. If the power headcannot restore the vacuum level to the defined initial threshold vacuumlevel in a defined amount of time, a catastrophic leak detection alarmis generated and the STP is shut down.

If the vacuum level in the outer annular space is restored to thedefined initial threshold vacuum level within a defined period of time,a precision leak detection test is performed. The sensing unit monitorsthe vacuum level in the outer annular space to determine if the vacuumlevel decays to a precision threshold vacuum level within a definedperiod of time, in which case a precision leak detection alarm isgenerated, and the STP may be shut down.

Once a catastrophic leak or precision leak detection alarm is generated,service personnel are typically dispatched to determine if a leak reallyexists, and if so, to take corrective measures. Tests are conducted todetermine if the leak exists in the vacuum tubing, in the sensing unit,or in the outer annular space.

The sensing unit also contains a liquid detection conduit. A liquiddetection sensor is placed inside the liquid detection conduit, whichmay be located at the bottom of the liquid detection conduit, so thatany liquid leaks captured in the outer annular space of the fuel pipingare stored and detected. The sensing unit and tank monitor can detectliquid in the sensing unit at certain times or at all times. If a liquidleak is detected by the tank monitor, the tank monitor will shut downthe STP if so programmed.

The tank monitor may be communicatively coupled to a site controllerand/or remote system to communicate leak detection alarms and otherinformation obtained by the sensing unit. The site controller may passinformation from the tank monitor onward to a remote system, and thetank monitor may communicate such information directly to a remotesystem.

Another parent disclosure extended the functionality of the other parentapplications by extending the vacuum generation and pressure sensing tothe riser pipe that connects the power head to the underground storagetank. The riser pipe is a double-walled pipe and the vacuum of the powerhead, along with the sensing system described above, are used to monitorthe interstitial space of the riser pipe.

The present invention takes the parent disclosures one step further.Specifically, the power head may be contained within a casing. Thepresent invention creates a vacuum in the space between the power headand the casing (also called the interior space of the casing). Thisvacuum may be created by the power head and a sensing unit as previouslydescribed may be used to monitor the vacuum levels in the interior spaceof the casing. In particular, the interior space of the casing isisolated from other interstitial spaces and monitored in isolation. If aleak is detected, an alarm may be generated and the activity of the STPmay be suspended until the leak is isolated and corrected.

Those skilled in the art will appreciate the scope of the presentinvention and realize additional aspects thereof after reading thefollowing detailed description of the invention in association with theaccompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is an underground storage tank, submersible turbine pump and fueldispenser system in a service station environment in the prior art;

FIG. 2 is a schematic diagram of the outer annular space of thedouble-walled fuel piping extending into the power head;

FIG. 3 is a schematic diagram of one embodiment of the sensingcomponents used in the present invention;

FIGS. 4A and 4B are flowchart diagrams illustrating one embodiment ofthe leak detection test of the present invention;

FIG. 5 is a flowchart diagram of a liquid leak detection test for oneembodiment of the present invention;

FIG. 6 is a flowchart diagram of a functional vacuum leak detection testfor one embodiment of the present invention that is carried out in atank monitor test mode;

FIG. 7 is a flowchart diagram of a functional liquid leak detection testfor one embodiment of the present invention that is carried out in atank monitor test mode;

FIG. 8 is a schematic diagram of a tank monitor communicationarchitecture;

FIG. 9 illustrates an exemplary embodiment of the double-walled riserpipe;

FIG. 10 illustrates a second embodiment of the double-walled riser pipewherein the vacuum and sensing are introduced to the interstitial spaceat the fittings;

FIG. 11 illustrates a third embodiment of the double-walled riser pipewherein the interstitial space of the double-walled riser pipe isfluidly connected to the interstitial space of the underground storagetank;

FIG. 12 illustrates a fourth embodiment of the double-walled riser pipewherein the interstitial space of the double-walled riser pipe isfluidly connected to a casing of the power head;

FIG. 13 illustrates an alternate embodiment of the present inventionwherein the casing of the power head includes a double-wall, and theinterstitial space thereof is subjected to the vacuum and sensing of thepresent invention;

FIG. 14 illustrates a first embodiment of a pipe fitting;

FIG. 15 illustrates a second embodiment of a pipe fitting; and

FIG. 16 illustrates an embodiment of the power head within a casing anda leak detection system associated therewith.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the invention and illustratethe best mode of practicing the invention. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the invention and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

FIGS. 1-15 represent the disclosures made in the parent applications.This background material may be helpful to understand some of thedetails of the creation of a vacuum in an interstitial space and thesensing that accompanies this vacuum that is used to determine if thereis a leak. The discussion of the present invention begins with thediscussion of FIG. 16; however, it should be appreciated that theteachings of the sensing element and the algorithms used to detect leakswith the sensing element are applicable to the embodiments introduced inFIG. 16.

FIG. 1 illustrates a fuel delivery system known in the prior art for aservice station environment. A fuel dispenser 1 0 is provided thatdelivers fuel 22 from an underground storage tank (UST) 20 to a vehicle(not shown). The fuel dispenser 10 is comprised of a fuel dispenserhousing 12 that typically contains a control system 13 and a display 14.The fuel dispenser 10 contains valves and meters (not shown) to allowfuel 22 to be received from underground piping and delivered through ahose and nozzle (not shown). More information on a typical fueldispenser 10 can be found in U.S. Pat. No. 5,782,275, assigned to sameassignee as the present invention, incorporated herein by reference inits entirety.

The fuel 22 that is dispensed by the fuel dispenser 10 is stored beneaththe ground in the UST 20. There may be a plurality of USTs 20 in aservice station environment if more than one type of fuel 22 is to bedelivered by fuel dispensers 10 in the service station. For example, oneUST 20 may contain high octane gasoline, another UST 20 may contain lowoctane gasoline, and yet another UST 20 may contain diesel fuel. The UST20 is typically a double-walled tank comprised of an inner vessel 23that holds the fuel 22 surrounded by an outer casing 25. The outercasing 25 provides an added measure of security to prevent leaked fuel22 from reaching the ground. Any leaked fuel 22 from a leak in the innervessel 23 will be captured in an annular space 27 that is formed betweenthe inner vessel 23 and the outer casing 25. This annular space is alsocalled an “interstitial space” 27. More information on USTs 20 inservice station environments can be found in U.S. Pat. No. 6,116,815,which is incorporated herein by reference in its entirety.

A submersible turbine pump (STP) 30 is provided to draw the fuel 22 fromthe UST 20 and deliver the fuel 22 to the fuel dispensers 10. An exampleof a STP 30 is the Quantum™ manufactured and sold by the Marley PumpCompany and disclosed at http://www.redjacket.com/guantum.htm. Anotherexample of a STP 30 is disclosed in U.S. Pat. No. 6,126,409,incorporated hereby by reference in its entirety. The STP 30 iscomprised of a power head 36 that incorporates a vacuum pump andelectronics (not shown). Typically, the vacuum pump is a venturi that iscreated using a portion of the pressurized fuel product, but the STP 30is not limited to such an embodiment. The power head 36 is fluidlyconnected to a column pipe 37 which is surrounded by a riser pipe 38that is mounted using a mount 40 connected to the top of the UST 20. Theriser pipe 38 extends downwardly from the power head 36 around thecolumn pipe 37. The column pipe 37 extends down into the UST 20 and isterminated with a boom 42 that is fluidly coupled to the fuel 22.

The boom 42 is coupled to a turbine housing 44 that contains a turbine,also called a “turbine pump” (not shown), both of which terms can beused interchangeably. When one or more fuel dispensers 10 in the servicestation are activated to dispense fuel 22, the STP 30 electronics areactivated to cause the turbine inside the turbine housing 44 to rotateto pump fuel 22 into the turbine housing inlet 46 and into the boom 42.The fuel 22 is drawn through the column pipe 37 in the riser pipe 38 anddelivered to the main fuel piping conduit 48. The main fuel pipingconduit 48 is coupled to the fuel dispensers 10 in the service stationwhereby the fuel 22 is delivered to a vehicle (not shown). If the mainfuel piping conduit 48 is a double-walled piping, the main fuel pipingconduit 48 will have an interstitial space 56 as well to capture anyleaked fuel.

Regulatory requirements require that any portion of main fuel pipingconduit 48 exposed to the ground be contained within a housing or otherstructure so that any leaked fuel 22 from the main fuel piping conduit48 is captured. This secondary containment is provided in the form of adouble-walled portion of main fuel piping conduit 48, as illustrated inFIG. 1. The double-walled portion of main fuel piping conduit 48contains an inner space 55 surrounded by an outer annular space 56formed by outer wall 54, referred to in the figures as “secondarycontainment” (the outer annular space 56 is sometimes also called hereinthe “interstitial space” 56). The terms “outer annular space” and“interstitial space” are well known interchangeable terms to one ofordinary skill in the art. The fuel 22 is carried in the inner space 55.In FIG. 1 and in prior art systems, the outer annular space 56 runsthrough the sump wall 32 and the inner space 55 terminates once insidethe sump wall 32 via clamping. This is because the sump wall 32 providesthe secondary containment of the inner space 55 for the portion the mainfuel piping conduit 48 inside the sump wall 32.

The power head 36 is typically placed inside a sump 31 so that any leaksthat occur in the power head 36 are contained within the sump 31 and arenot leaked to the ground. A sump liquid sensor 33 may also be providedinside the sump 31 to detect any such leaks so that the sump 31 can beperiodically serviced to remove any leaked fuel. The sump liquid sensor33 may be communicatively coupled to a tank monitor 62, site controller64, or other control system via a communication line 81 so that liquiddetected in the sump 31 can be communicated to an operator and/or analarm be generated. An example of a tank monitor 62 is the TLS-350manufactured by the Veeder-Root Company. An example of a site controller64 is the G-Site® manufactured by Gilbarco Inc. Note that any type ofmonitoring device or other type of controller or control system can beused in place of a tank monitor 62 or site controller 64.

The main fuel piping conduit 48, in the form of a double-walled pipe, isrun underneath the ground in a horizontal manner to each of the fueldispensers 10. Each fuel dispenser 10 is placed on top of a fueldispenser sump 16 that is located beneath the ground underneath the fueldispenser 10. The fuel dispenser sump 16 captures any leaked fuel 22that drains from the fuel dispenser 10 and its internal components sothat such fuel 22 is not leaked to the ground. The main fuel pipingconduit 48 is run into the fuel dispenser sump 16, and a branch conduit50 is coupled to the main fuel piping conduit 48 to deliver the fuel 22into each individual fuel dispenser 10. The branch conduit 50 istypically run into a shear valve 52 located proximate to ground level sothat any impact to the fuel dispenser 10 causes the shear valve 52 toengage, thereby shutting off the fuel dispenser 10 access to fuel 22from the branch conduit 50. The main fuel piping conduit 48 exits thefuel dispenser sump 16 so that fuel 22 can be delivered to the next fueldispenser 10, and so on until a final termination is made. A fueldispenser sump sensor 18 is typically placed in the fuel dispenser sump16 so that any leaked fuel from the fuel dispenser 10 or the main fuelpiping conduit 48 and/or branch conduit 50 that is inside the fueldispenser sump 16 can be detected and reported accordingly.

FIG. 2 illustrates a fuel delivery system in a service stationenvironment according to one embodiment of the present invention. Theouter wall 54 provided by the outer annular space 56 of the main fuelpiping conduit 48 is run through the sump 31 and all the way to thepower head 36, as illustrated. In this manner, the pressure or vacuumlevel created by the power head 36 can also be applied to the outerannular space 56 of the main fuel piping conduit 48 to detect leaks viamonitoring of the vacuum level in the outer annular space 56, as will bediscussed later in this patent application. The terms “pressure” and“vacuum level” are used interchangeably herein. One or more pressuresensors 60 may be placed in the outer annular space 56 in a variety oflocations, including but not limited to inside the sump 31, power head36, and the outer annular space 56 inside the fuel dispenser sump 16.

In the embodiment illustrated in FIG. 2, the outer annular space 56 ofthe main fuel piping conduit 48 is run inside the power head 36 so thatany fuel 22 that has leaked into the outer annular space 56 can bedetected by the sump liquid sensor 33 and/or be collected in the sump 31for later evacuation. By running the outer annular space 56 of the mainfuel piping conduit 48 inside the power head 36, it is possible togenerate a vacuum level in the outer annular space 56 from the same STP30 that draws fuel 22 from the UST 20 via the boom 42. Any method ofaccomplishing this function is contemplated by the present invention.One method may be to use a siphon system in the power head 36 to createa vacuum level in the outer annular space 56, such as the siphon systemdescribed in U.S. Pat. No. 6,223,765, assigned to Marley Pump Companyand incorporated herein by reference its entirety. Another method is todirect some of the vacuum generated by the STP 30 from inside the boom42 to the outer annular space 56. The present invention is not limitedto any particular method of the STP 30 generating a vacuum level in theouter annular space 56.

FIG. 3 illustrates another embodiment of running the outer annular space56 of the main fuel piping conduit 48 only into the sump 31 rather thanthe outer annular space 56 being run with the inner space 55 into thepower head 36. A vacuum tubing 70 connects the outer annular space 56 tothe power head 36. Again, as discussed for FIG. 2 above, the power head36 is coupled to the outer annular space 56, such as using directcoupling to the power head 36 (as illustrated in FIG. 2), or using avacuum tubing 70 (as illustrated in FIG. 3) as a vacuum generatingsource to create a vacuum level in the outer annular space 56. Whetherthe configuration of coupling the power head 36 to the outer annularspace 56 is accomplished by the embodiment illustrated in FIG. 2, FIG.3, or other manner, the vacuum level monitoring and liquid leakdetection aspects of the present invention described below and withrespect to a sensing unit 82 illustrated in FIG. 3 is equally applicableto all embodiments.

FIG. 3 also illustrates a sensing unit 82, which may be provided eitherinside or outside the sump 31 and/or power head 36, that monitors thevacuum level in the outer annular space 56 of the main fuel pipingconduit 48. If the outer annular space 56 cannot maintain a vacuum levelover a given period of time after being pressurized, this is indicativethat the outer wall 54 contains a breach or leak. In this instance, ifthe inner space 55 were to incur a breach or leak such that fuel 22reaches the outer annular space 56, this same fuel 22 would also havethe potential to reach the ground through the breach in the outer wall54. Therefore, it is desirable to know if the outer wall 54 contains abreach or leak when it occurs and before a leak or breach occurs in theinner space 55, if possible, so that appropriate notifications, alarms,and measures can be taken in a preventive manner rather than after aleak of fuel 22 to the ground occurs. It is this aspect of the presentinvention that is described below.

The sensing unit 82 is comprised of a sensing unit controller 84 that iscommunicatively coupled to the tank monitor 62 via a communication line81. The communication line 81 is provided in an intrinsically safeenclosure inside the sump 31 since fuel 22 and or fuel vapor may bepresent inside the sump 31. The sensing unit controller 84 may be anytype of microprocessor, micro-controller, or electronics that is capableof communicating with the tank monitor 62. The sensing unit controller84 is also electrically coupled to a pressure sensor 60. The pressuresensor 60 is coupled to a vacuum tubing 70. The vacuum tubing 70 iscoupled to the power head 36 so that the power head 36 or other portionof the STP 30 can be used as a vacuum source to generate a vacuum level,which may be a positive or negative vacuum level, inside the vacuumtubing 70. The vacuum tubing 70 is also coupled to the outer annularspace 56 of the main fuel piping conduit 48. A check valve 71 may beplaced inline to the vacuum tubing 70 if it is desired to prevent theSTP 30 from ingressing air to the outer annular space 56 of the mainfuel piping conduit 48.

An isolation valve 88 may be placed inline with the vacuum tubing 70between the sensing unit 82 and the outer annular space 56 of the mainfuel piping conduit 48 to isolate the sensing unit 82 from the outerannular space 56 for reasons discussed later in this application. Avacuum control valve 90 is also placed inline to the vacuum tubing 70between the pressure sensor 60 and the power head 36 of the STP 30. Thevacuum control valve 90 is electrically coupled to the sensing unitcontroller 84 and is closed by the sensing unit controller 84 when it isdesired to isolate the vacuum source of the STP 30 from the outerannular space 56 during leak detection tests, as will be described inmore detail below. The vacuum control valve 90 may be asolenoid-controlled valve or any other type of valve that can becontrolled by sensing unit controller 84.

An optional differential pressure indicator 98 may also be placed in thevacuum tubing 70 between the power head 36 of the STP 30 and sensingunit 82 on the power head 36 side of the vacuum control valve 90. Thedifferential pressure indicator 98 may be communicatively coupled to thetank monitor 62. The differential pressure indicator 98 detects whethera sufficient vacuum level is generated in the vacuum tubing 70 by thevacuum source of the STP 30. If the differential pressure indicator 98detects that a sufficient vacuum level is not generated in the vacuumtubing 70 by the vacuum source of the STP 30, and a leak detection testfails, this may be an indication that a leak has not really occurred inthe outer annular space 56. The leak detection may have been a result ofthe vacuum source of the STP 30 failing to generate a vacuum in thevacuum tubing 70 in some manner. The tank monitor 62 may use informationfrom the differential pressure indicator 98 to discriminate between atrue leak and a vacuum level problem with the vacuum source of the STP30 in an automated fashion. The tank monitor 62 may also generate analarm if the differential pressure indicator 98 indicates that thevacuum source of the STP 30 is not generating a sufficient vacuum levelin the vacuum tubing 70. Further, the tank monitor 62 may first checkinformation from the differential pressure indicator 98 after detectinga leak, but before generating an alarm, to determine if the leakdetection is a result of a true leak or a problem with the vacuum levelgeneration by the vacuum source of the STP 30.

In the embodiments further described and illustrated herein, thedifferential pressure indicator 98 does not affect the tank monitor 62generating a leak detection alarm. The differential pressure indicator98 is used as a further information source when diagnosing a leakdetection alarm generated by the tank monitor 62. However, the scope ofthe present invention encompasses use of the differential pressureindicator 98 as both an information source to be used after a leakdetection alarm is generated and as part of a process to determine if aleak detection alarm should be generated.

The sensing unit 82 also contains a liquid detection conduit 92. Theliquid detection conduit 92 is fluidly coupled to the outer annularspace 56. The liquid detection conduit 92 is nothing more than a conduitthat can hold liquid and contains a liquid detection sensor 94 so thatany liquid that leaks in the outer annular space 56 will be containedand cause the liquid detection sensor 94 to detect a liquid leak, whichis then reported to the tank monitor 62. The liquid detection sensor 94may contain a float (not shown) as is commonly known in one type ofliquid detection sensor 94. An example of such a liquid detection sensor94 that may be used in the present invention is the “Interstitial Sensorfor Steel Tanks,” sold by Veeder-Root Company and described on thewebsite http://www.veeder-root.com/dynamic/index.cfm?pageID=175, filedwith the Information Disclosure Statement, incorporated herein byreference in its entirety.

The liquid detection sensor 94 is communicatively coupled to the sensingunit controller 84 via a communication line 65. The sensing unitcontroller 84 can in turn generate an alarm and/or communicate thedetection of liquid to the tank monitor 62 to generate an alarm and/orshut down the STP 30. The liquid detection sensor 94 can be locatedanywhere in the liquid detection conduit 92, but is preferably locatedat the bottom of the liquid detection conduit 92 at its lowest point sothat any liquid in the liquid detection conduit 92 will be pulledtowards the liquid detection sensor 94 by gravity. If liquid, such asleaked fuel 22, is present in the outer annular space 56, the liquidwill be detected by the liquid detection sensor 94. The tank monitor 62can detect liquid in the outer annular space 56 at certain times or atall times, as programmed.

If liquid leaks into the liquid detection conduit 92, it will be removedat a later time, typically after a liquid leak detection alarm has beengenerated, by service personnel using a suction device that is placedinside the liquid detection conduit 92. In an alternative embodiment, adrain valve 96 is placed inline between the liquid detection conduit 92and the sump 31 that is opened and closed manually. During normaloperation, the drain valve 96 is closed, and any liquid collected in theliquid detection conduit 92 rests at the bottom of the liquid detectionconduit 92. If liquid is detected by the liquid detection sensor 94 andservice personnel are dispatched to the fueling environment, the servicepersonnel can drain the trapped liquid by opening the drain valve 96,and the liquid will drain into the sump 31 for safe keeping and so thatthe system can again detect new leaks in the sensing unit 82. When it isdesired to empty the sump 31, the service personnel can draw the liquidout of the sump 31 using a vacuum or pump device.

Against this backdrop, the functional operation of these components isbetter explicated. The parent disclosures teach that the presentinvention is capable of performing two types of leak detections tests:precision and catastrophic. A catastrophic leak is defined as a majorleak where a vacuum level in the outer annular space 56 changes veryquickly due to a large leak in the outer annular space 56. A precisionleak is defined as a leak where the vacuum level in the outer annularspace 56 changes less drastically than a vacuum level change for acatastrophic leak.

FIGS. 4A and 4B provide a flowchart illustration of the leak detectionoperation of the sensing unit that, according to one embodiment of thepresent invention, performs both the catastrophic and precision leakdetection tests for the outer wall 54 of the main fuel piping conduit48. The tank monitor 62 directs the sensing unit 82 to begin a leakdetection test to start the process (step 100). Alternatively, a testmay be started automatically if the vacuum level reaches a predefinedthreshold. In response, the sensing unit controller 84 opens the vacuumcontrol valve 90 (step 102) so that the STP 30 is coupled to the outerannular space 56 via the vacuum tubing 70. The STP 30 provides a vacuumsource and pumps the air, gas, and/or liquid out of the vacuum tubing 70and the outer annular space 56, via its coupling to the vacuum tubing70, after receiving a test initiation signal from the tank monitor 62.The STP 30 pumps the air, gas or liquid out of the outer annular space56 until a defined initial threshold vacuum level is reached orsubstantially reached (step 104). The tank monitor 62 receives thevacuum level of the outer annular space 56 via the measurements from thepressure sensor 60 communication to the sensing unit controller 84. Thisdefined initial threshold vacuum level is −15 inches of Hg in oneembodiment of the present invention, and may be a programmable vacuumlevel in the tank monitor 62. Also, note that if the vacuum level in theouter annular space 56 is already at the defined initial thresholdvacuum level or substantially close to the defined initial vacuumthreshold level sufficient to perform the leak detection test, steps 102and 104 may be skipped.

After the vacuum level in the vacuum tubing 70 reaches the definedinitial threshold vacuum level, as ascertained by monitoring of thepressure sensor 60, the tank monitor 62 directs the sensing unitcontroller 84 to deactivate the STP 30 (unless the STP 30 has beenturned on for fuel dispensing) and to close the vacuum control valve 90to isolate the outer annular space 56 from the STP 30 (step 106). Next,the tank monitor 62 monitors the vacuum level using vacuum levelreadings from the pressure sensor 60 via the sensing unit controller 84(step 108). If the vacuum level decays to a catastrophic thresholdvacuum level, which may be −10 inches of Hg in one embodiment of thepresent invention and also may be programmable in the tank monitor 62,this is an indication that a catastrophic leak may exist (decision 110).The sensing unit 82 opens the vacuum control valve 90 (step 112) andactivates the STP 30 (unless the STP 30 is already turned on for fueldispensing) to attempt to restore the vacuum level back to the definedinitial threshold vacuum level (−15 inches of Hg in the specificexample) (step 114).

Continuing to FIG. 4B, the tank monitor 62 determines if the vacuumlevel in the outer annular space 56 has lowered back down to the definedinitial threshold vacuum level (−15 inches of Hg in the specificexample) within a defined period of time, which is programmable in thetank monitor 62 (decision 116). If not, this is an indication that amajor leak exists in the outer wall 54 of the main fuel piping conduit48 or the vacuum tubing 70, and the tank monitor 62 generates acatastrophic leak detection alarm (step 118). The tank monitor 62, if soprogrammed, will shut down the STP 30 so that the STP 30 does not pumpfuel 22 to fuel dispensers 10 that may leak due to the breach in theouter wall 54 (step 120), and the process ends (step 122). An operatoror service personnel can then manually check the integrity of the outerannular space 56, vacuum tubing 70 and/or conduct additional leakdetection tests on-site, as desired, before allowing the STP 30 to beoperational again. If the vacuum level in the outer annular space 56does lower back down to the defined initial threshold vacuum levelwithin the defined period of time (decision 116), no leak detectionalarm is generated at this point in the process.

Back in decision 110 (shown in FIG. 4A), if the vacuum level did notdecay to the defined initial threshold vacuum level (−10 inches of Hg inspecific example), this is also an indication that a catastrophic leakdoes not exist. Either way, if the answer to decision 110 is no, or theanswer to decision 116 is yes, the tank monitor 62 goes on to perform aprecision leak detection test since no catastrophic leak exists.

For the precision leak detection test, the tank monitor 62 directs thesensing unit controller 84 to close the vacuum control valve 90 if it isnot already closed (step 124). Next, the tank monitor 62 determines ifthe vacuum level in the outer annular space 56 has decayed to aprecision threshold vacuum level within a defined period of time, bothof which may be programmable (decision 126). If not, the tank monitor 62logs the precision leak detection test as completed with no alarm (step136), and the leak detection process restarts again as programmed by thetank monitor 62 (step 100).

If the vacuum level in the outer annular space 56 has decayed to aprecision threshold vacuum level within the defined period of time, thetank monitor 62 generates a precision leak detection alarm (step 128).The tank monitor 62 determines if the tank monitor 62 has beenprogrammed to shut down the STP 30 in the event of a precision leakdetection alarm (decision 130). If yes, the tank monitor 62 shuts downthe STP 30, and the process ends (step 134). If not, the STP 30 cancontinue to operate when fuel dispensers are activated, and the leakdetection process restarts again as programmed by the tank monitor 62(step 100). This is because it may be acceptable to allow the STP 30 tocontinue to operate if a precision leak detection alarm occurs dependingon regulations and procedures. Also, note that both the precisionthreshold vacuum level and the defined period of time may beprogrammable at the tank monitor 62 according to levels that are desiredto be indicative of a precision leak.

Once a catastrophic leak or precision leak detection alarm is generated,service personnel are typically dispatched to determine if a leak reallyexists, and if so, to take corrective measures. The service personnelcan close the isolation valve 88 between the sensing unit 82 and theouter annular space 56 to isolate the two from each other. The servicepersonnel can then initiate leak tests manually from the tank monitor 62that operate as illustrated in FIGS. 4A and 4B. If the leak detectiontests pass after previously failing and after the isolation valve 88 isclosed, this is indicative that some area of the outer annular space 56contains the leak. If the leak detection tests continue to fail, this isindicative that the leak may be present in the vacuum tubing 70connecting the sensing unit 82 to the outer annular space 56, or withinthe vacuum tubing 70 in the sensing unit 82 or the vacuum tubing 70between sensing unit 82 and the power head 36 of the STP 30. Closing ofthe isolation valve 88 also allows components of the sensing unit 82 andvacuum tubing 70 to be replaced without relieving the vacuum in theouter annular space 56 since it is not desired to recharge the systemvacuum and possibly introduce vapors or liquid into the outer annularspace 56 since the outer annular space 56 is under a vacuum and willdraw in air or liquid if vented.

FIG. 5 is a flowchart diagram of a liquid leak detection test performedby the tank monitor 62 to determine if a leak is present in the outerannular space 56. The liquid leak detection test may be performed by thetank monitor 62 on a continuous basis or at periodic times, depending onthe programming of the tank monitor 62. Service personnel may also causethe tank monitor 62 to conduct the liquid leak detection test manually.

The process starts (step 150), and the tank monitor 62 determines if aleak has been detected by the liquid detection sensor 94 (decision 152).If not, the tank monitor 62 continues to determine if a leak has beendetected by the liquid detection sensor 94 in a continuous fashion. Ifthe tank monitor 62 does determine from the liquid detection sensor 94that a leak has been detected, the tank monitor 62 generates a liquidleak detection alarm (step 154). If the tank monitor 62 has beenprogrammed to shut down the STP 30 in the event of a liquid leakdetection alarm being generated (decision 156), the tank monitor 62shuts down the STP 30 (if the STP 30 is on for fuel dispensing) (step158), and the process ends (step 160). If the tank monitor 62 has notbeen programmed to shut down the STP 30 in the event of a liquid leakdetection alarm being generated, the process just ends without takingany action with respect to the STP 30 (step 160).

FIG. 6 is a flowchart diagram that discloses a functional vacuum leakdetection test performed to determine if the sensing unit 82 canproperly detect a purposeful leak. If a leak is introduced into theouter annular space 56, and a leak is not detected by the sensing unit82 and/or tank monitor 62, this is an indication that some component ofthe leak detection system is not working properly.

The process starts (step 200), and a service person programs the tankmonitor 62 to be placed in a functional vacuum leak detection test mode(step 202). Next, a service person manually opens the drain valve 96 orother valve to provide an opening in the outer annular space 56 orvacuum tubing 70 so that a leak is present in the outer annular space 56(step 204). The tank monitor 62 starts a timer (step 206) and determineswhen the timer has timed out (decision 208). If the timer has not timedout, the tank monitor 62 determines if a leak detection alarm has beengenerated (decision 214). If not, the process continues until the timertimes out (decision 208). If a leak detection alarm has been generated,as is expected, the tank monitor 62 indicates that the functional vacuumleak detection test passed and that the leak detection system is workingproperly (step 216) and the process ends (step 212).

If the timer has timed out without a leak being detected, this isindicative that the functional vacuum leak detection test failed (step210) and that there is a problem with the system, which could be acomponent of the sensing unit 82 and/or tank monitor 62. Note thatalthough this functional vacuum leak detection test requires manualintervention to open the drain valve 96 or other valve to place a leakin the outer annular space 56 or vacuum tubing 70, this test could beautomated if the drain valve 96 or other valve in the outer annularspace 56 or vacuum tubing 70 was able to be opened and closed undercontrol of the sensing unit 82 and/or tank monitor 62.

FIG. 7 illustrates a functional liquid leak detection test that can beused to determine if the liquid detection system of the presentinvention is operating properly. The liquid detection sensor 94 isremoved from the liquid detection conduit 92 and submerged into acontainer of liquid (not shown). Or in an alternative embodiment, apurposeful liquid leak is injected into the liquid detection conduit 92to determine if a liquid leak detection alarm is generated. If a liquidleak detection alarm is not generated when liquid is placed on theliquid detection sensor 94, this indicates that there has been a failureor malfunction with the liquid detection system, including possibly theliquid detection sensor 94, the sensing unit 82, and/or the tank monitor62.

The process starts (300), and the tank monitor 62 is set to a mode forperforming the functional liquid leak detection test (step 302). Thevacuum control valve 90 may be closed to isolate the liquid detectionconduit 92 from the STP 30 so that the vacuum level in the outer annularspace 56 and sensing unit 82 is not released when the drain valve 96 isopened (step 304). Note that this is an optional step. Next, the drainvalve 96, if present, or outer annular space 56 is opened in the system(step 306). The liquid detection sensor 94 is either removed and placedinto a container of liquid, or liquid is inserted into the liquiddetection conduit 92, and the drain valve 96 is closed (step 308). Ifthe tank monitor 62 detects a liquid leak from the sensing unit 82(decision 310), the tank monitor 62 registers that the functional liquidleak detection test has passed (step 312). If no liquid leak is detected(decision 310), the tank monitor 62 registers that the functional liquidleak detection test failed (step 316). After the test is conducted, ifliquid was injected into the liquid detection conduit 92 as the methodof subjecting the liquid detection sensor 94 to a leak, either the drainvalve 96 is opened to allow the inserted liquid to drain and then closedafterwards for normal operation, or a suction device is placed into theliquid detection conduit 92 by service personnel to remove the liquid(step 313), and the process ends (step 314).

Note that although this functional liquid leak detection test requiresmanual intervention to open and close the drain valve 96 and to inject aliquid into the liquid detection conduit 92, this test may be automatedif a drain valve 96 is provided that is capable of being opened andclosed under control of the sensing unit 82 and/or tank monitor 62 and aliquid could be injected into the liquid detection conduit 92 in anautomated fashion.

FIG. 8 illustrates a communication system whereby leak detection alarmsand other information obtained by the tank monitor 62 and/or sitecontroller 64 from the communication line 81 may be communicated toother systems if desired. This information, such as leak detectionalarms for example, may be desired to be communicated to other systemsas part of a reporting and dispatching process to alert servicepersonnel or other systems as to a possible breach or leak in the outerwall 54 of the main fuel piping conduit 48.

The tank monitor 62 that is communicatively coupled to the sensing unit82 and other components of the present invention via the communicationline 81 may be communicatively coupled to the site controller 64 via acommunication line 67. The communication line 67 may be any type ofelectronic communication connection, including a direct wire connection,or a network connection, such as a local area network (LAN) or other buscommunication. The tank monitor 62 may communicate leak detectionalarms, vacuum level/pressure level information and other informationfrom the sensing unit 82 to the site controller 64. Alternatively, thesensing unit 82 may communicate this with the site controller 64directly via the communication line 78. The site controller 64 may befurther communicatively coupled to a remote system 72 to communicatethis same information to the remote system 72 from the tank monitor 62and the site controller 64 via a remote communication line 74. Theremote communication line 74 may be any type of electronic communicationconnection, such as a PSTN, or network connection such as the Internet,for example. The tank monitor 62 may also be directly connected to theremote system 72 using a remote communication line 76 rather thancommunication through the site controller 64. The site controller 64 mayalso be connected to the communication line 81 so that theaforementioned information is obtained directly by the site controller64 rather than through the tank monitor 62.

Note that any type of controller, control system, sensing unitcontroller 84, site controller 64 and remote system 72 may be usedinterchangeably with the tank monitor 62 as described in thisapplication and the claims of this application.

The vacuum creation technology and sensing technology of the parentdisclosures may also be applied to the riser pipe 38 and the power head36 as will be explained with reference to FIGS. 9-13. Specifically, theparent application discloses the process for detecting leaks in theriser pipe 38. This leak detection can be done in conjunction with theleak detection of the other parent disclosures. For example, a holisticsystem might detect leaks in the underground storage tank 20, the riserpipe 38, the power head 36, and the main fuel piping conduit 48.Specifically, a vacuum may be created by the vacuum siphon of the powerhead 36 and applied to some or all of these regions. Then, the leakdetection algorithms of FIGS. 4A-7 may be applied to these regions sothat leaks may be detected. This arrangement may help comply with newregulations being imposed on fueling environments. Even if thisarrangement is not required by regulation or statute, fuelingenvironment operators may wish to install such systems to increase thelikelihood of detecting a leak to minimize environmental damage and/orprevent loss of inventory.

Turning to FIG. 9, the sump 31 is illustrated. As explained above, thepower housing 36 sits atop the riper pipe 38. While FIG. 9 shows theriser pipe 38 completely contained within the sump 31, it is possiblethat a portion of the riser pipe 38 may be external to the sump 31 as isillustrated in FIG. 3. In the embodiment of FIG. 9, the riser pipe 38has an interior column pipe 37, an interstitial space 402, and anexterior wall 404. A pressure sensor 60 may be positioned within theinterstitial space 402. Further, the vacuum tubing 70 may be connectedto the interstitial space 402 through the sensing unit 82 or directly asneeded or desired. If the sensing unit 82 is used, then it is possibleto omit the pressure sensor 60 within the interstitial space 402. Asillustrated, the exterior wall 404 is crimped at each end of the riserpipe 38 so that the interstitial space 402 is isolated from otherinterstitial spaces such as areas 27 and 56. While crimping is onespecifically contemplated treatment for the end of the riser pipe 38,other sealing treatments may also be used and still be within the scopeof the present invention. Such seals can be made by welding, potting,and the like as is well understood in the industry. By isolatinginterstitial space 402 in this manner, the pressure sensor 60 may detecta leak within the confines of interstitial space 402 independently ofleaks in other interstitial spaces 27 and 56. It should be appreciatedthat the processes of detecting the leak described with reference toFIGS. 2-8 would be used to detect the leak in interstitial space 402.

In contrast to the embodiment of FIG. 9, wherein the vacuum tubing 70fluidly connects to the interstitial space 402 through the exterior wall404, FIG. 10 illustrates that the vacuum tubing 70 may alternativelyconnect to the interstitial space 402 through a fitting 406 or 406A (orboth) positioned at either end of the riser pipe 38. The use of afitting 406 or 406A allows the vacuum tubing to 70 to connect to theinterstitial space 402 without creating a breach in exterior wall 404.This further precludes the necessity for custom made riser pipes 38 withspecialized elements that allow the vacuum tubing 70 to be connectedthereto. Two embodiments of exemplary fittings are explained below inFIGS. 14 and 15. A brief summary is provided here for convenience. Thefittings described in this application contemplate a number of differentoptions. In one embodiment, the fitting allows the connection of theinterstitial space 402 to the vacuum tubing 70. Additionally, thefitting-has threads that are adapted to be threaded into a complementaryelement such as the power head 36. The fitting lies flush against theelement, and may capture any leaks through the threads and convey theseleaks to the interstitial space 402.

A third embodiment of the leak detection system of the parentapplication is illustrated in FIG. 11 wherein the interstitial space 402is fluidly connected to the interstitial space 27 of the undergroundstorage tank 20. Specifically, the interstitial spaces 27 and 402 areconnected through the fitting 408, which is designed to allow fluidcommunication therethrough. The vacuum tubing 70 is connected to theinterstitial space 402 through the exterior wall 404, through thefitting 408 (not shown, but suggested by fitting 406 in FIG. 10), orcould alternatively be connected to the interstitial space 27 asexplained in the previously incorporated related application Ser. No.10/390,346. Pressure sensors 60 may be positioned in the interstitialspace 402 or in the sensing unit 82 as needed or desired. It should beappreciated that the processes of detecting the leak described withreference to FIGS. 2-8 would be used to detect the leak in interstitialspace 402. This embodiment allows a single pressure sensor 60 or sensingunit 82 to detect a leak in interstitial spaces 27 and 402. This mayallow equipment costs to be reduced, albeit at the expense ofresolution. Specifically, if these interstitial spaces 27 and 402 arefluidly connected, it may be difficult to determine if a detected leakis in the interstitial space 27 or the interstitial space 402 without avisual inspection.

As yet another alternative, the interstitial space 402 of FIG. 12 mayextend into a casing 400 for the power head 36. Note that the casing 400corresponds closely to the casing body described in the previouslyincorporated '765 patent (labeled casing body 12, with cover 22 in the'765 patent). In this embodiment, the vacuum tubing 70 may be locatedentirely within the casing 400. The sensing unit 82 may likewise bepositioned within the casing 400 and connected to the vacuum siphon ofthe power head 36 via the vacuum tubing 70. In this embodiment, it ispossible that the exterior wall 404 may be threaded into a complementarythreaded portion of the power head 36, while the column pipe 37 extendsinto the fuel flow area 410 of the power head 36. It should beappreciated that the processes of detecting the leak described withreference to FIGS. 2-8 would be used to detect the leak in interstitialspace 402. This embodiment allows a single sensor 60 or sensing unit 82to detect leaks in the interstitial space 402 and the interior of thecasing 400. This may allow equipment costs to be reduced, albeit at theexpense of resolution. Specifically, if these interstitial spaces arefluidly connected, it may be difficult to determine if a detected leakis in the interstitial space 402 or within the casing 400.

Another variation of the present invention is illustrated in FIG. 13,wherein the casing 400 has an interstitial space 412 delimited byinterior wall 414 and exterior wall 416. A pressure sensor 60 may bepositioned in the interstitial space 412, and the interstitial space 412may be connected to the vacuum-creating siphon of the power head 36through vacuum tubing 70 as previously explained. It should beappreciated that the processes of detecting the leak described withreference to FIGS. 2-8 would be used to detect the leak in interstitialspace 412. This embodiment allows a sensor 60 or sensing unit 82 todetect leaks in the casing 400 or in the power head 36. This may helpcomply with environmental regulations or minimize environmental damage.Further, this embodiment helps provide complete double-walled protectionfor every element within the fueling environment.

Turning now to FIGS. 14 and 15, two embodiments of the fitting 406 areshown. Double-walled piping, which may be the riser pipe 38, the mainfuel piping conduit 48, or the like, is fluidly connected to areceptacle 490, such as the power head 36, the sump 31, or the like. Tohelp effectuate this connection, a fitting 500 is secured to the end ofthe double-walled piping. The fitting 500 may be secured to thedouble-walled piping with glue, crimping, welding, threaded elements, orthe like, as is well understood in the industry. Fitting 500 includes aninterior space 502 through which fuel flows. Interior space 502 isdelimited by interior wall 504. Interior wall 504 is surrounded by outerwall 506. Interstitial space 508 is fluidly connected to theinterstitial space of the double-walled piping.

Interior wall 504 has threads 510 on a terminal end thereof. In theexemplary embodiment, the threads 510 are male threads adapted to bereceived by complementary female threads 494 in the wall 492 of thereceptacle 490.

Outer wall 506 has a flange 512 on a terminal end thereof. Flange 512has a groove 514 that is adapted to receive an o-ring 516 therein. Anupper surface 518 of flange 512 lies flush with an exterior surface 496of the wall 492, and o-ring 516 causes a seal to be formed between thereceptacle 490 and the fitting 500. By forming this seal, any fluid thatleaks through the threads 510 and 494 is captured in interstitial space508.

A fluid channel 520 is delimited by outer wall 506 and protuberance 522.Vacuum tubing (not shown, but, for example, vacuum tubing 70) may besnap-fit over or otherwise connected to protuberance 522. Vacuum tubingmay then be connected to a vacuum source, such as the siphon area of theSTP, or the vacuum tubing may be connected to another interstitial spacethat is already under vacuum. This connection to an interstitial spacealready under vacuum will create a vacuum in interstitial space 508 formonitoring or other purposes as needed or desired. In this manner, theinterstitial space 508 can be monitored up to the point of the threads510 of the fitting 500 rather than only up to the point of theconnection between the fitting 500 and the double-walled piping.Further, the fluid channel 520 can be provided at the fitting 500instead of in the double-walled piping.

An alternate embodiment for the fitting 500 is illustrated in FIG. 15.Instead of the protuberance 522 and channel 520, the embodiment of FIG.15 has a channel 524 that extends through the wall 492 of the receptacle490. In this manner, the interstitial space 508 is extended through thefitting 500 to the receptacle 490 so that a vacuum source within thereceptacle 490 can be used to generate a vacuum in the interstitialspace 508. An example would be an STP generating a vacuum in a riserpipe. Alternatively, if the interstitial space 508 is already under avacuum, the channel 524 can be used to create a vacuum within thereceptacle 490. Other variations of fittings are also possible.

The present invention builds on the teachings of the parent applicationsby monitoring the interior space of the casing 400. While the parentapplications disclosed monitoring the interior space of the casing 400in conjunction with the interstitial space 402 of the riser pipe 38, thepresent invention monitors the interior space alone. This providesgreater leak detection resolution and may be done to insure that thecasing 400 is not leaking or that the power head 36 is not leaking. Asdescribed in the incorporated '765 patent, the casing 400 is fluidtight. The present invention is illustrated in FIG. 16.

Specifically, the casing 400 encloses the power head 36 and is isolatedfrom the interstitial space 402 of the riser pipe 38 via a cap 430positioned on the bottom of the casing 400. The space between the innersurface 432 of casing 400 and the power head 36 is the interior space434 of the casing 400. Vacuum tubing 70 terminates within the interiorspace 434 and is connected to the siphon line within the power head 36as previously described. Alternatively, the vacuum tubing 70 may beconnected to the turbine pump within the boom 42 as previouslydescribed. In either case, a vacuum is created in the interior space434.

A pressure sensor 60 may be positioned in the interior space 434 so thatpressure levels of the interior space 434 may be measured.Alternatively, the sensing unit 82 may be associated with the vacuumtubing 70 as previously discussed. Once the vacuum is established withinthe casing 400, the processes of detecting the leak described withreference to FIGS. 2-8 would be used to detect the leak in interiorspace 434.

It is possible that this arrangement may eliminate the need for the sump31 or provide additional leak detection and alarm generation so that theleaks may be detected in a timely fashion with the resolution requiredto isolate the leak. Armed with this information, the leaks may becorrected before any environmental damage is sustained and so allregulatory and statutory rules are followed by the fueling environments.

As used herein, the term “vacuum generating means” includes the siphonline within the power head 36 and the vacuum generated by the pumpwithin boom 42. Also, structural equivalents of these elements are meantto be included in the term.

The various embodiments presented herein allow for double-walledcontainment to be positioned in virtually every location within thefueling environment. Further, the present invention teaches a method ofleak detection for each of these situations so as to avoid contaminatingthe environment with leaking fuel.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present invention. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

1-23. (canceled)
 24. A method for detecting a leak in a casing for apower head of a submersible turbine pump, said casing having an interiorspace, said method comprising: creating a vacuum level in the interiorspace of the casing using the submersible turbine pump as a vacuumsource; sensing the vacuum level in the interior space using a pressuresensor; and monitoring the vacuum level in the interior space todetermine if a leak exists in the casing.
 25. The method of claim 24,further comprising coupling the vacuum source to the interior spaceusing vacuum tubing.
 26. The method of claim 25, wherein said step ofcoupling the vacuum source to the interior space using vacuum tubingfurther comprises coupling the vacuum tubing to the power head.
 27. Themethod of claim 24, wherein the step of sensing the vacuum level in theinterior space using a pressure sensor comprises sensing the vacuumlevel with a pressure sensor positioned in the interior space.
 28. Themethod of claim 24, further comprising the step of sensing whetherliquid is present in the interior space using a liquid detection sensor.29. The method of claim 28, further comprising generating a liquid leakdetection alarm if said liquid detection sensor senses liquid in theinterior space.
 30. The method of claim 29, further comprising disablingsaid submersible turbine pump if said liquid detection sensor sensesliquid in the interior space.
 31. The method of claim 24, furthercomprising closing a vacuum control valve to isolate said submersibleturbine pump from the interior space before performing said step ofmonitoring the vacuum level in the interior space.
 32. The method ofclaim 24, further comprising determining if said vacuum source isdrawing a sufficient vacuum level in the interior space.
 33. The methodof claim 32, further comprising generating an alarm if said vacuumsource is not drawing a sufficient vacuum level in the interior space.34. The method of claim 24, wherein creating a vacuum level in theinterior space of the casing using the submersible turbine pump as avacuum source comprises generating a siphon using a venturi with thepower head.
 35. The method of claim 24, wherein creating a vacuum levelin the interior space of the casing using the submersible turbine pumpas a vacuum source comprises creating a defined initial threshold vacuumlevel in the interior space of the casing using the submersible turbinepump as a vacuum source after receiving a test initiation signal. 36.The method of claim 35, further comprising generating a leak detectionalarm if the vacuum level in the interior space of the casing using thesubmersible turbine pump as a vacuum source cannot be created to reachthe defined initial threshold vacuum level.
 37. The method of claim 24,further comprising determining if the vacuum level in the interior spacehas decayed to a threshold vacuum level from a defined initial thresholdvacuum level.
 38. The method of claim 37, further comprising creating avacuum level in the interior space of the casing using the submersibleturbine pump as a vacuum source to attempt to lower the vacuum level inthe interior space back down to the defined initial threshold vacuumlevel if the vacuum level in the interior space decays to the definedinitial threshold vacuum level.
 39. The method of claim 38, furthercomprising determining if the vacuum level in the interior space lowersto the defined initial threshold vacuum level within a defined amount oftime.
 40. The method of claim 39, further comprising generating an alarmif the vacuum level in the interior space does not lower to the definedinitial threshold vacuum level within the defined amount of time.